Medication infusion pump

ABSTRACT

An extracorporeal medication infusion device provides a precise infusion rate of a liquid medication into a human or animal body. The infusion device includes a permanent portion which has a case, a battery, a programmable electronic controller, and an electromagnetic solenoid core and solenoid coil for providing an actuation force. The infusion device also includes a disposable portion which includes a reservoir filled with a liquid medication that is to be dispensed and a pump for pumping the medication from the reservoir into the user&#39;s body. The pump includes a pump chamber and a piston connected to an electromagnetic armature for altering the volume of the pump chamber in response to the actuation force.

This is a division of application Ser. No. 252,779 filed Apr. 10, 1981,now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates generally to medication infusion devices,and more particularly to a miniature extracorporeal medication infusiondevice for precisely and conveniently dispensing controlled quantitiesof a liquid medicine into a human or animal body.

Liquid medications (which, for purposes of this patent application,means any liquid that is to be injected into a human or animal body fortherapeutic or diagnostic purposes) have been traditionally administeredby a hypodermic syringe. If multiple doses of the liquid medication arerequired, the multiple doses are typically administered at timedintervals of several days or several hours.

More recently, it has been recognized that the benefits of certainliquid medications may be enhanced by administering the liquidmedication in extremely small dosages on a frequent basis. Medicationinfusion devices which have been designed for this purpose are disclosedin U.S. Pat. Nos. 4,191,181, 4,150,672, 4,215,689, and 3,858,581.Additionally, other devices have been provided which administer aconstant flow rate of liquid medication, such as shown in U.S. Pat. No.4,201,207.

SUMMARY OF THE INVENTION

The present invention departs from these and other prior art devices byproviding an extracorporeal medication infusion device which permitsprecise control of the dosage of liquid medication that is administeredand that provides ease and convenience of use.

According to the principles of the invention, the extracorporealmedication infusion device includes a reusable portion and a disposableportion. The reusable portion includes a rigid case, a battery powersupply, and a programmable electronic controller. The reusable portionof the infusion device also includes an electromagnetic solenoid coreand an electromagnetic solenoid coil which receives an electrical signalfrom the controller and provides a magnetic actuating force.

The disposable portion of the infusion device includes a collapsablereservoir for storing the liquid medication. The disposable portion alsoincludes a disposable pump for pumping the liquid medication from thereservoir to the human or animal body to which the liquid medication isto be provided. The pump includes a pumping chamber having inlet andoutlet check valves, and an electromagnetic armature provides a means tovary the volume of the chamber in response to the magnetic actuatingforce of the coil.

The disposable portion and the reusable portion each also includeprecise alignment surfaces arranged in predetermined positions. When thedisposable portion is releasably secured in the case of the reusableportion, the alignment surfaces of the disposable portion engagecorresponding alignment surfaces of the reusable portion. In thismanner, the armature on the disposable portion is precisely aligned withand spaced a predetermined distance from the core in the reusableportion. When the electrical signal is provided by the controller to thecoil, the magnetic force then provides movement of the armature throughthis predetermined distance. When the electrical signal is terminated, aleaf spring returns the armature to its rest position.

This arrangement of applicant's invention assures that the movement ofthe armature and corresponding stroke of the pump will always be thesame, when the disposable portions are changed on a periodic basis whilethe device is being used. Additionally, because the pump utilizes thepositive action of a leaf spring to return the pump to the rest positionat the completion of each pump cycle, the return stroke and outputpressure of the pump is also precisely controlled. Still further, theinfusion device provided by the instant invention is convenient and easyto use, and provides the option to the user of either filling thereservoir pump from a separate vial of liquid medication or purchasingthe disposable portion in a prefilled condition for maximum convenienceand ease of use.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects and advantages of the invention will be morereadily apparent upon an understanding of the preferred embodiment ofthe invention shown in the drawings, wherein:

FIG. 1 is a perspective view of the extracorporeal medication infusiondevice according to the principles of the invention;

FIG. 2 is a perspective view of the disposable portion of the deviceshown in FIG. 1;

FIG. 3 is an enlarged cross-sectional view taken along reference viewline 3--3 in FIG. 2;

FIG. 4 is a cross-sectional view taken along reference view line 4--4 inFIG. 1;

FIG. 5 is a perspective view of a spring that is used to maintainalignment of the disposable portion and the reusable portion of thedevice shown in FIG. 1;

FIG. 6 is an enlarged view of the inlet check valve shown in FIG. 3;

FIG. 7 is a still further enlarged perspective view of the check valveshown in FIG. 6;

FIG. 8 is an enlarged perspective view of the pump housing for thedevice, with the armature shown in phantom;

FIG. 9 is a side-elevational view of the armature for the disposableportion shown in FIG. 2; and

FIG. 10 is an enlarged perspective view of the solenoid core for thereusable portion of the device shown in FIG. 4.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in greater detail, FIG. 1 illustrates anextracorporeal medication infusion device 10. The medication infusiondevice 10 is of small size (approximately 21/2 inches long, 1 inch wide,and 1/2 inch thick) and light weight (approximately 21/2 ounces) and isadapted to be carried in the user's pocket or taped or strapped to theuser's body. The medication infusion device 10, as explained in furtherdetail below, carries a reservoir of liquid medication and provides ameans for dispensing the liquid medication into the user's body at aprogrammed rate.

Referring now to FIGS. 1 and 4 together, the medication infusion device10 includes a reusable portion 11 and a dispensable portion 12. Thereusable portion 11 is adapted to be utilized repeatedly over a periodof several years for dispensing liquid medication to the body of theuser. The disposable portion 12 is adapted to dispense a predeterminedquantity of liquid medication which it carries, and to then be discardedand replaced with a new disposable portion carrying a new quantity ofthe liquid medication.

Referring still to FIGS. 1 and 4, the reusable portion 11 includes arigid plastic case 15. The case 15 includes a top wall 16, a bottom wall17, end walls 18, and internal dividing walls 19. The walls 16-19 areall of approximately the same thickness and same material. The top wall16 includes a removable panel 20 for providing access to the disposableportion 12 and a removable panel 21 for providing access to a battery 22which provides a source of electrical power for the medication infusiondevice 10. The removable panels 20 and 21 are secured in place by asuitable detent (not shown) in a well known manner.

The reusable portion 11 also includes a programmable electroniccontroller 23 which receives electrical power from the battery 22 andwhich provides electrical energy to a solenoid 24.

The solenoid 24 includes a coil 25 which is energized by the controller23 on a programmed basis and an electromagnetic core 26. The core 26, asshown in greater detail in FIG. 10, is made of magnetic material (suchas a martensitic stainless steel) and is of a generally E-shapedconfiguration. The core 26 includes end walls 27, 28 and 29 which facetoward an armature as explained in greater detail below. The end walls27 and 29 are co-planar, and the end wall 28 may be recessed slightlyfrom the plane in which the walls 27 and 29 are disposed to facilitaterelease of the armature after actuation of the coil 25.

Four identical alignment bars 30, only three of which may be seen inFIG. 10, are secured at similar locations on opposite sides of the core26. The alignment bars 30 are each of non-magnetic material (such as anaustenitic stainless steel) and are welded to the core 26 in theposition shown in FIG. 10. The alignment bars 30 each include a precisealignment surface 31, and the alignment surfaces 31 are co-planar. Theplane in which the alignment surfaces 31 are disposed is spaced apredetermined distance from the plane in which the core surfaces 27 and29 are disposed, and the perpendicular distance between these two planesis the stroke of the pump, as explained in further detail below.

Referring back to FIG. 1, the medication infusion device 10 alsoincludes a replaceable needle and connecting tube assembly 34. Theassembly 34 is connected to the disposable portion 12 by a threadedconnection 35. The needle and connecting tube assembly 34 may thereforebe disconnected from the disposable portion 12 when the disposableportion 12 is to be replaced.

Referring now to FIGS. 1, 2 and 3 together, the disposable portion 12includes a reservoir 41, a pump 42, and an electromagnetic armature 43.The reservoir 41 includes a collapsable plastic bag 44 that is securedwithin a cylindrical plastic housing 45 and sealingly attached to aplastic end wall 46. The collapsable bag 44 is filled by injecting theliquid medicine that is to be dispensed through a septum 47.

The pump 42 includes a pump housing 49 which defines an inlet passage50, an outlet passage 51, and a pump chamber 52. The pump 42 alsoincludes check valves 53 placed in the inlet and outlet passages 50 and51. The check valves 53, as shown in greater detail in FIGS. 6 and 7,are of one-piece plastic construction and include a base 54. In thepreferred embodiment, the check valves are of a thermoplastic carbonatelinked polymer such as that sold under the trademark "Lexan" by GeneralElectric Co., or of an acrylic polymer resin such as that sold under thetrademark "Cryolite G-20" by Cry/Ro Industries. An annular seat 55projects from one side of the base 54 to provide sealing engagement withan adjacent surface in the passage. A plurality of leaf spring portions56 project from a central hub of the base 54 and provide a spring forceto urge the seat 55 against its adjacent surface. A plurality of axiallyextending stops 57, which are disposed between adjacent ones of thesprings 56, project from the base 54 in a direction opposite to the seat55 to control the travel of the seat 55 away from its adjacent surfacewhen the check valve 53 is opened.

Referring now to FIGS. 3, 8 and 9 together, the pump 42 further includesa piston 61 which reciprocates in a bore that intersects the pumpchamber 52 in a direction perpendicular to the axis of the passages 50and 51. The piston 61 is of plastic construction and is sealed againstthe walls of the bore in which it is disposed by an o-ring seal 62. Theo-ring seal 62 is dimensioned and arranged so that it is compressed inthe groove in the outer peripheral surface of the piston 61 and so thatit does not slide relative to either the piston 61 or the bore. Instead,the o-ring 62 is of sufficient elasticity, and the movement of thepiston 61 is sufficiently small, that elastic deformation of the o-ring62 is sufficient to accommodate the full stroke of the piston 61 in thebore.

The electromagnetic armature 43, which is of magnetic material such asmartensitic stainless steel, includes a stem portion projecting from itsbottom surface which is received with an interference fit in a bore inthe piston 61. In this manner, the armature 43 is rigidly connected tothe piston 61 so that movement of the armature 43 causes correspondingmovement of the piston 61. Two suitable spring rests 63, only one ofwhich is shown in FIGS. 8 and 9, project laterally in oppositedirections from the armature 43. Two identical leaf springs 64 areprovided on each lateral side of the pump housing 49 and act between thepump housing 49 and the spring rests 63 to urge the piston 61 to itsrest position shown in the drawings.

As best shown in FIG. 8, the pump housing 49 also includes alignmentsurfaces 67. The alignment surfaces 67 are co-planar with one anotherand are co-planar with the top surface of the armature 43. When the pump42 is manufactured, this co-planar relationship may be accomplished byinitially making the alignment surfaces 67 project beyond the topsurface of the armature 43, and then, after the armature 43 and springs64 are installed in the pump housing 49, melting or grinding thesurfaces 67 to a co-planar relationship with the top surface of thearmature 43.

Referring now to FIGS. 3 and 4 together, the disposable portion 12 isreleasably assembled in the case 15 by opening the removable panel 20.The disposable portion 12 is then inserted into the case 15 in a mannersuch that the alignment surfaces 67 of the pump housing 49 (FIG. 8)contact the alignment surfaces 31 of the core 26 (FIG. 10). This contactis established and maintained by a suitable leaf spring 68 (see FIGS. 4and 5). An elastomeric grommet 69, which is frictionally received in anopen ended slot in the case 15 when the cover 20 is removed, secures theremovable portion 12 against axial movement relative to the reusableportion 11.

The materials for the reusable portion 11 and disposable portion 12 areselected from commercially available thermoplastic materials to provideadequate strength and rigidity, resistance to chemicals, and ease ofmanufacturing. In the preferred embodiment, the case 15 is of anacrylonitrile-butadiene-styrene copolymer (ABS), the resevoir 44 is of asuitable flexible thermoplastic urethane resin, and the pump housing 49and piston 61 are of an acrylic polymer resin such as that sold underthe trademark "Cryolite G-20" by Cy/Ro Industries.

When it is desired to pump the liquid medication from the collapsablereservoir 44 to the outlet passage 51 and to the needle and tubeassembly 34, the controller 23 provides an electrical current toenergize the coil 25. This causes the armature 43 to move upwardly asviewed in the drawings until the top surface of the armature 43 engagesthe surfaces 27 and 29 of the core 26. This causes the piston 61 to moveupwardly to increase the volume of the chamber 52. As the volume of thechamber 52 increases, the check valve 53 in the inlet passage 50 opensto permit liquid medication to flow from the reservoir 44 into the pumpchamber 52. When this electrical current is interrupted, the coil 25 isde-energized and the springs 64 push the armature 43 and piston 61downwardly as viewed in the drawings to decrease the volume of thechamber 52. This causes the check valve 53 in the outlet passage 51 toopen to permit flow of the liquid medicine from the pump chamber 52 tothe needle and tube assembly 34. When the liquid medication in thereservoir 44 is nearly depleted, the user opens the removable panel 20,removes the existing disposable portion 12, and inserts a new disposableportion 12 with a full reservoir of liquid medication.

What is claimed is:
 1. An integral one-piece check valve for use with acooperating valve surface, said check valve comprising:a generally diskshaped base; an annular valve seat on one side of said base; a pluralityof spring fingers that extend radially from a central hub disposed onthe other side of said base; and a plurality of axially extending stopmembers disposed on said other side of said base, said stop membersextending axially between adjacent ones of said radially extendingspring fingers.
 2. An integral one-piece check valve comprising:anannular valve surface facing in one direction; a plurality of springfingers that extend radially from a central hub; and a plurality of stopmembers extending axially in a direction opposite said one directionbetween adjacent ones of said radially extending spring fingers.